1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, and an image forming apparatus and a process unit having the electrophotographic photosensitive member.
2. Related Background Art
Hitherto, in electrophotographic recording processes, electrophotographic photosensitive members are gradually contaminated by components of transfer mediums and discharge products formed at the time of charging, not only because of toners remaining after transfer but also as a result of repeated use. Such contamination of electrophotographic photosensitive members results in a decrease in their surface electrical resistivity thus causing disturbance of electrostatic images and also a melt adhesion of toner to the surfaces of electrophotographic photosensitive members to cause serious damage to images.
Accordingly, a measure conventionally taken is to intentionally abrade the surface of an electrophotographic photosensitive member with a cleaning blade or the like to make the surface of the electrophotographic photosensitive member always new so that good images can always be obtained. This enables maintenance of good images since the surfaces of electrophotographic photosensitive members are always renewed.
However, contaminants adhered to the surfaces of electrophotographic photosensitive members become more difficult to remove as the photosensitive members are repeatedly used. Hence, in conventional photosensitive members, their surfaces are excessively abraded from initials use so that the contaminants are removed even after the use of photosensitive members are used for a long period of time. In other words, an attempt to more completely remove contaminants results in a shorter lifetime of electrophotographic photosensitive members.
Thus, there is a problem that an attempt to maintain stable images makes their lifetime short because of an excessive abrasion of photosensitive layers of electrophotographic photosensitive members. On the other hand, an attempt to make their lifetime longer by less abrasion of the photosensitive layers makes it impossible to maintain good images.
Meanwhile, a method for detecting the layer thickness of a photosensitive layer is proposed (e.g., Japanese Patent Application Laid-open No. 5-223513). This is a method in which electric currents flowing when charges are eliminated from a photosensitive member brought into a charged state (or the photosensitive member brought into a charge-eliminated state is charged) are detected and the capacitance as a capacitor is measured therefrom to calculate the layer thickness of a photosensitive layer. In this way, appropriate maintenance of photosensitive members can be made.